Top 10 Considerations For Automotive EMC Chamber Design .

Top 10 Considerationsfor Automotive EMCChamber Designand Testing

TOP 10 CONSIDERATIONS FOR AUTOMOTIVEEMC CHAMBER DESIGNAND TESTINGFollowing is our Top 10 list of the most important things you need to consider whendeveloping or refining an automotive EMC chamber and test design. This resourcewill help you avoid the most common mistakes, and what you should consider toensure a more successful project. This quick and concise guide covers standards,DUT considerations, automotive industry trends – including autonomous vehicles and more!1. Know your automotive EMC standards – what standards do you want to test inaccordance with to attract customers/meet your company’s requirements?The major automotive EMC standards are issued by the Society of Automotive Engineers (SAE),the International Electrotechnical Committee (IEC), the International Standards Organization(ISO), the European Community (EC) and the United Nations Economic Commission for Europe(UNECE). The most commonly referenced standards for full vehicle and electronic subassemblies(ESA) are the CISPR standards issued by the IEC, such as CISPR 25 and CISPR 12, followed closelyby the ISO standards 11451 and 11452. These standards apply to traditional, hybrid and electricvehicles and specify the test distances and methods required to validate a product’s performance.This dictates the size of the test range required, placement of anechoic absorber (if needed) and testapparatus needed to perform various tests. Each standard has its own requirements so researchthem carefully to ensure your chamber will comply with your standards of interest. The table belowsummarizes the most commonly referenced EMC standards that cover vehicles in their scope. Inaddition to the commercial EMC standards noted above, there are also military standards, such asMIL-STD-461, which also applies to automotive subsystems and vehicles.StandardIssuing BodiesApplicabilityVehicleTest CoveredESAISO 11451ISOYesNoRSISO RESAE J551SAEYesNoRE & RSSAE J1113SAENoYesRE & RS95/54/ECECYesYesRE & RS2004/104/ECECYesYesRE & RSECE Reg. 105UNECEYesYesRE & RSMIL-STD-461DoDYesYesRE & RSBe aware that manufacturers also issue company specific standards, such as those published byGeneral Motors, Ford, and Fiat Chrysler Automobiles (FCA), etc. These company specific standardseach have their own nuances that should be addressed if they are a targeted customer of your testchamber.2

2. Consider the size of the device under test (DUT) as full vehicle DUTs vs component levelDUTs influence the chamber size and cost.This may be stating the obvious, but within full vehicles, there are many sizes. Some chambers aresized to test 56 seat passenger busses, while others are sized to test “smart cars” which seat twopassengers. Some vehicles are heavier than others which impacts floor loading requirements. Theradiating elements used can also have an impact on the chamber size, especially those used for lowfrequency high field strength testing. Components likewise can vary in size. Every square yard/meter ofa chamber adds to the overall cost so careful consideration of the size of your DUT, antennas and testrange will result in the most cost effective chamber.3. Consider the frequency range when looking at test chambers for ADS, V2X, and OTAapplications.Another cost driver of a chamber size is a factor of the frequency range. Advanced Driver AssistanceSystems (ADAS), Connected Vehicles including vehicle-to-vehicle (V2V), vehicle-to-infrastructure(V2I), and Vehicle-to-Cloud (V2C) as well as Over-the-Air (OTA) operational frequencies all featuredifferent frequencies. Automotive test chambers need to address various frequency ranges, currentlyincluding: FM Radio from 70 MHz HD radio Cellular from 700 MHz to 60 GHz (3G, 4G,LTE, 5G) Satellite from 1.6 GHz WiFi from 2.4/5.8 GHz DSRC 5.9 GHz RADAR 24 GHz/79 GHzResearch the features of your DUT to specify the desiredfrequency range testing needed. The overall scope of vehicletesting is expected to experience ongoing development so considerthe upgrade potential of the chamber and system design.Images courtesy of the U.S. Department of Transportation3

4. Become familiar with and follow the automotive industry trends to be prepared forfuture test requirements.Automobiles have changed considerably over the years as shown below. From the early 1960swhen cruise control was introduced to the current trend towards autonomous vehicles, the testenvironment for automotive vehicles and components has changed, and continues to change!The rapid development of advanced automotive features and the trend toward autonomy is drivingthe need for more sophisticated automotive EMC design and test scenarios. Vehicle platformscontinue to become increasingly more complex with propulsion, entertainment and safety relatedsystems all having to function reliably without impacting safety or the legacy communicationsinfrastructure. The safety and reliability requirements for autonomous vehicles will rival, and insome cases surpass, the requirements for aerospace and military systems. Plan your chamber designto take into account the capabilities needed for future automotive test requirements, especially thoserelated to communications.Image by Dllu - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid 634504464

5. Consider a retrofit/upgrade of an existing chamber.If you have an existing full vehicle test chamber, depending on the size of the chamber, desired DUT sizeand applicable test standards, you may be able to upgrade your chamber. This may involve replacing currentanechoic absorber with new or different absorber, adding a test apparatus to the interior of your chamberto cover an extended range of measurements as shown above, or possibly increasing the size of the chamberdoor. It is worth exploring if a chamber upgrade/retrofit will expand your automotive test capabilities whilealso saving time and money.6. If a new chamber, evaluate design options for various component or full vehicle test needs.This presents the best opportunity to design for your current and future testing needs. Available budget isalways a limitation but avoid making this the limiting factor in the initial discussions on overall scope. Theintended use of the chamber can drive several design elements. A commercial test lab’s need for customerthroughput and flexibility is different to a manufacturer’s R&D needs. Addressing and incorporating thenew chamber design with the parent building design and construction also has many cost and scheduleadvantages. These and the other items listed in this “Top 10” could drive subtle differences in overallchamber design which could be considered for a new chamber.7. Be aware of the challenges associated with current and quickly developing sensor andantenna technologies extending traditional automotive EMC testing.Automotive EMC test chambers may be designed for more complex test capabilities,such as those involving elements of Advanced Driver Assistance Systems (ADAS), RadioDetection and Ranging (RADAR) and Light Detection and Ranging (LIDAR). Antennaarrays, as well as signal and protocol simulators, may be installed in the chamber to test theperformance of these capabilities. This results in a combination chamber for both EMCand antenna (wireless) measurements, commonly referred to as a hybrid chamber. Today’smodern vehicles include many antennas that are mounted in various locations inside andoutside of the vehicle. These antennas are highly integrated with the automotive body foraesthetic, practical and performance reasons. Performance must be verified as an integralpart of the vehicle. A hybrid chamber facilitates these measurements by enabling EMC,wireless Over-the-Air (OTA), and antenna pattern measurements.5

8. Don’t overlook anechoic absorber – consider options for optimal performance,durability, and cost effectiveness.Traditional EMC chambers have been designed over the years with RF absorber optimized toprovide a cost effective level of performance over the 28 MHz to 2.5 GHz frequency range. Dedicatedantenna measurement and RADAR cross section (RCS) chambers which typically cover frequenciesfrom 100 MHz to over 100 GHz use a different type of RF absorber, with different performance andin some cases, different RF power dissipation requirements. Hybrid chambers (those capable of EMCand antenna pattern measurements) are increasingly utilized since their dual purpose drives sometest efficiencies. The RF absorber treatment must be based on the overall frequency range of thechamber and in the case of the tapered shape chamber, where different test zones are employed withthe benefit of a reduced footprint, the absorber layout could be critical. An example of a full vehiclehybrid chamber is shown below.6

9. Don’t underestimate the importance of a dynamometer.Dynamometers are an essential component of a full vehicle test chamber. They are expensive, have along lead time, and require careful integration with the chamber to ensure the chamber performance isnot compromised. There are two major types of dynamometers:1. A chassis ‘Dyno’ which is full size vehicle dyno to simulate road driving load.2. A motor ‘Dyno’ which is a smaller device connected directly to a motor during componenttesting to provide a representative load to the motor assembly. It is typically capable of measuringthe torque at various speeds while applying drive or a breaking or drag resistance.A typical test set up for a motor dynamometer is shown above.There are many types of dynamometers available with advantages and disadvantages for specific testtypes. Selection is based on a number of parameters and features: Available torque range Maximum speed Minimum speed Maximum power dissipation Response time Inertia profile Test scenarioIn addition, dynamometers used for E-motor testing need more operating options, such as highermaximum speed rating than combustion engines, the ability to operate in both directions, and theability to drive and brake. Installing a dynamometer also requires planning to accommodate thesupport equipment. Consider and select your dynamometer at the beginning of your chamber designplanning.7